The present work investigates the nature of dry-friction whip and whirl through
experimental and numerical methods. Efforts of the author, Dyck, Pavalek, and
coworkers enabled the design and construction of a test rig that demonstrated and
recorded accurately the character of multi-mode dry-friction whip and whirl. These tests
examined steady state whip and whirl characteristics for a variety of rub materials and
clearances. Results provided by the test rig are unparalleled in quality and nature to those
seen in literature and possess several unique characteristics that are presented and
discussed.
A simulation model is constructed using the Texas A and M University (TAMU)
Turbomachinery Laboratory rotordynamic software suite XLTRC2 comprised of tapered
Timoshenko beam finite elements to form multiple degree of freedom rotor and stator
models. These models are reduced by component mode synthesis to discard highfrequency
modes while retaining physical coordinates at locations for nonlinear
interactions. The interaction at the rub surface is modeled using a nonlinear Hunt and
Crossley contact model with coulomb friction. Dry-friction simulations are performed
for specific test cases and compared against experimental data to determine the validity
of the model. These comparisons are favorable, capturing accurately the nature of dryfriction
whirl.
Experimental and numerical analysis reveals the existence of multiple whirl and
whip regions spanning the entire range of frequencies excited during whirl, despite
claims of previous investigations that these regions are predicted by Black's whirl
solution, but are not excited in simulations or experiments. In addition, spectral analysis
illustrates the presence of harmonic sidebands that accompany the fundamental whirl
solution. These sidebands are more evident in whip, and can excite higher-frequency whirl solutions. Experimental evidence also shows a strong nonlinearity present in the
whirl frequency ratio, which is greater than that predicted by the measured radius-toclearance
ratio at the rub location. Results include whirl frequencies 250% of that
predicted by the measured radius-to-clearance ratio.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2008-08-44 |
| Date | 16 January 2010 |
| Creators | Wilkes, Jason C. |
| Contributors | Childs, Dara W. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis |
| Format | application/pdf |
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